Blankenstein Castle was built originally in 1227-1243 by Adolf I, Count of Mark. It was further developed over the course of 200 years by the Counts of the Mark. By 1425, Blankenstein was one of the most important castles in the county. In 1614, shortly before the Thirty Years' War, it was occupied by Spanish troops. From 1637, the castle fell into disrepair so that, in September 1662, Frederick William, Elector of Brandenburg ordered its demolition. Only the tower and parts of the curtain wall remained.
In 1860, the owner of the ruin, the employer, Gustav vom Stein, began to rebuild the castle and established a factory there. The property has belonged to the city of Bochum since 1922, but the town is looking for an alternative due to the costs. From 1957 to 1959, most of the buildings of the 19th century were pulled down, but some still remain.
The tower can still be visited and offers a good view over Bochum and the Kemnader Lake.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.